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Auscultatory findings in Mitral regurgitation

Heart sounds in mitral regurgitation
S1 ( first heart sound) is absent, soft, or it may be buried in the holosystolic murmur of chronic MR.
S2 (second heart sound).In those patients with severe MR, the premature closure of aortic valve may, result in wide but physiologic splitting of S2 .
S3 (third heart sound) in patients with mitral regurgitation after the aortic valve closure sound low pitched S3 may occur.This is heard at the end of rapid filling phase of left ventricle.
S3 in mitral regurgitation is caused by the sudden tensing of the papillary muscles, chordae tendineae, and valve leaflets.
S4 (fourth heart sound) may sometimes audible in acute severe MR if the patient is in sinus rhythm.

Murmur in mitral regurgitation
The most characteristic auscultatory finding in chronic severe MR is a systolic murmur of at least grade III/VI intensity.
In chronic MR it is usually holosystolic.In patients with acute severe MR it is decrescendo and ends in mid to late systole.
In chronic MR the systolic murmur is most prominent at the apex and  it radiates to the axilla. If the MR is due to ruptured chordae tendineae or due to primary involvement of the posterior mitral leaflet with prolapse or flail, then the murmur may radiate anteriorly and is transmitted to the base of the heart and, it may be confused with the AS murmur.
If the MR is due to ruptured chordae tendineae, the resulting  systolic murmur may have a cooing or “sea gull” quality.
MR murmur due to  flail leaflet may produce a murmur that has a musical quality. 
The systolic murmur of chronic MR (not due to MVP) is increased  by isometric exercise (handgrip) but the murmur is reduced during the strain phase of the Valsalva maneuver because it  decrease left ventricular preload.
PSM in MR may sometime be followed by a short, rumbling, mid-diastolic murmur, even if there is no structural MS.